Telegraph repeater



Feb. 2v1, 1939. w, w. CRAMER' ET AL TELEGRAPH REPEATER Filed Aug. 30,1935 2 Sheets-Sheet 2 G. C. C 0MM/NGS A TTORNEV Patented Feb. 21, 1939PATENT OFFICE 2,147,690 TELEGRAPH REPEATER Walter W. Cramer, Rutherford,and George C. Cummings, Orange, N. J., assignors to Bell TelephoneLaboratories,

Incorporated, New

York, N. Y., a corporation of New York Application August so, 1935,serial No. 38,528

21 Claims.

'This invention relates to telegraph repeaters, and more particularly,to telegraph repeaters of the balanced type in which one relay must beheld inoperative While another relay transmits signal impulses throughthe Winding of the inactive relay.

An object of the invention is to prevent the inactive relay from beingoperated by line discharges when the active relay is operating.

Another object is to provide a repeater of simple design which may beeffectively operated in conjunction with any one of a plurality ofcomparatively high capacity lines, such as long subscribers loopcircuits. o Another object of the invention is to arrange for thecounteraction of line surges through a repeater relay Without thenecessity of increasing the line current beyond that used in ordinarypractice.

The present day tendency is to interconnect telegraph subscribersthrough svvitchboards which are equipped with repeaters. Therten'dencyis, furthermore, to use longer and longer subscribers loop circuits andto include the conductors for such loops in cables so that theircapacity to ground, as Well as their mutual capacity, becomes quiteappreciable. The discharge surges from the 'e line, consequently, arebecoming more and more pronounced and it is becoming necessary toprovide against their effect upon the relay operations.

When ,a marking potential is applied to a high capacity line, theso-called marking surge acts to charge the line to a given potential,both with respect to ground and with respect to the return conductor.This surge is in a direction such that the inactive relay is held tomarking. When a spacing potential is applied to the line through theline Winding of the inactive relay, a surge in the opposite direction orspacing surge takes place to discharge the line with respect to ground.This surge tends to operate the inactive relay to spacing, which, ofcourse, is not desired. In certain types of repeater circuits theseconditions are reversed.

In accordance With a feature of the invention, a uni-lateral device isconnected in circuit With the inactive relay in such a manner that itwill prevent the relay from kicking off during the spacing surgereferred to above.

In accordance with a further feature of the invention, the unilateraldevice is'associated With an impedance to form an asymmetric multiplenetwork which provides two paths, one forvthe normal current and one fora transient current.

be the surge impulse or a 'counter-eifective transient impulse, Y l o YThe invention Will now Abe described as y'applied in 'diler'ent mannersto a typical telegraph vrepeater circuit and reference Will be made tothe attahed drawings, ih 'Whichv Figs. 1, 2, and 3 show a half 'duplex4repeater of the balanced ltype in which the unidirectional device isassociated With the lille Winding Of the inactive relay in differentmanners, and A Figs. 4 and 5 show the device associated with thebalancing 'v's'rinding of the inactive relay. In Figs. 1 to 4,inclusive, the invention is illustrated inl connection with a,Ysubscribers loop, Whereas in Fig. 5 the invention is illustrated inconnection with a composite telephone line.

In`the drawings, only enoughy ofnthe repeater station is 'shown inthevarious iguresoto facilit'ate the'understandng of the principles andoperatioris of the invention. Thus, in each repeater only those partsare shown which cooperate with one line or loop circuit, it beingunderstood that for the purposes of thelinvention the connections to theother line circuit may be madein'any desirable manner, and may bemadevin the same manner as those illustrated. l L n Theembodimentsutoovvhich the rinvention will be applied,` while `beingpreferred, are merely given as examples; other Ways or rmodifications inwhich the advantages and features of the invention may be utilized willbe obvious to one skilled in this art. v Y

In orderv thatuthe operation of the invention may be clearly understood,theline circuit shown each of the circuit arrangementsl in the drawingsvvill be assumed to be of considerable length and to be composedpracticallyentirely of va pair v of cable (on'ducjrsk enclosed by a leadsheath. The line circuit will thus have appreciable mutual, distributedeapacitanee between thel two conductor'sand also'vv grounded distributedcapacitance between each conductor and the cable sheath. Thesecapacitances are diagrammatically illustrated in the drawings by dottedcondensers.

Referring now particularly to Fig. 1, the send-- ing relay |0| ofrepeater R is actuated in any suitable manner and transmits positive andnegative impulses through the upper or line winding of receiving relay|02 and over the line circuit I 05, |06 to actuate the distantsubscribers station S, it being a requirement of the circuit that thearmature of receiving relay |02 be held Vfirmly on its right-hand ormarking contact while pulses are being transmitted from sending relay|0|. The distributed capacitance between line conductor |05 and groundis represented by condensers ||0 and and between conductor 06 and groundby condensers ||2 and H3, and the mutual distributed capacitance betweenconductors |05 and |00 is represented by condensers ||4 and H5.

The subscribers station S may be equipped with standard teletypewriterapparatus and thus will have a receiving winding responsive to incomingsignals'for operation of the translating or recording device, andtransmitting or distributor contacts responsive to actuation of thekeyboard to transmit impulses into the line circuit.

VWith the armature of relay |0| on its righthand contact, as shown, amarking impulse is sent over the line to actuate receiving apparatus atstation S. This marking circuit is traced from positive battery throughthe right-hand contacts of relay |09, through the upper winding of relay|02, resistance |03, conductor |05, station S, conductor |00, tonegative battery through variable resistance |08. A unidirectionaldevice |04 is connected in parallel with the upper winding Vof Y relay|02 and resistance |03 but is poled in a direction so that very littleor no current flows through it during the marking impulse. Anothercircuit involving the lower winding of relay |02 is traced from positivebattery through the righthand contacts of relay |0| through the lowerwinding of relay |02 to ground through balancing network H0. With thesame number of turns in the windings of relay |02, the current in thelower winding is about one-half of that in the upper winding, and tendsduring marking condition to move the armature to spacing.

When .sending relay |0| closes its left-hand contacts, negative batteryis connected to negative battery over the line circuit described aboveand the current through the lower winding of relay |02 is reversed tohold the armature to marking as the line current becomes zero. However,the'line capacities ||0 and will now be charged to a negative Apotentialwith respect to ground and the capacities ||4 and ||5 will dischargethroughVV the line winding of relay |02. Thisy transient currentin theupper winding of relay |02 would tend to operate the relay to break itsright-hand contacts were it not for the fact that the unidirectionaldevice 00 is connected in such a way thatthe major part of the transientcurrent 'is shunted through it instead of traversing the upper windingof relay |02 and resistance |03. By this means, the reversed flux whichwould ordinarily be generated by the upper winding of relay |02 isinsufficient to overpower that of the lower winding and cause thearmature of relay |02 to leave its right-hand or marking contact.

When the line circuits described above are again closed to markingpotential, condensers I0, H4 and H5 will again be charged to positivepotential and the charging current will pass with its full strengththrough the upper winding of relay |02. Ihis causes a transientcondition in relay |02 during which the upper winding is more powerfulthan the lower winding. However, the additional ux generated by thistransient current is in a direction to hold the armature relay |02 morermly on its right-hand or marking contact and no diiiculty isexperienced upon the charge of the line capacity on the marking impulse.

Fig. 2 shows an arrangement Very similar in its action to that of Fig. 1except that a unidirectional impedance network consisting of resistance220 and unidirectional device 204, is inserted in series with the linecircuit instead of being connected as a shunt path for the upper windingof the receiving relay as shown in Fig. 1.

In Fig. 2, the transmitting circuit for the marking impulse is tracedfrom positive battery through the right-hand cont-acts of sending relay20|, the upper winding of relay 202, resistance 203, resistance 220 inparallel with unidirectional device 204, line conductor 205, station S,line conductor 206, to negative battery through variable resistance 208.When this condition was first established, the line current was in adirection to meet a low resistance path through unidirectional device204 and a heavy transient current, due to the reversal of charges oncondensers 2|0 and 2|| and to charging of condensers 2|4 and 2|5 whichrepresent the line distributed capacity, traversed the upper winding ofrelay 202 in a direction to cause the latter relay to hold itsright-hand contacts rmly closed. When sendingrelay 20| reverses thedirection of current in the line, however, the unidirectional device 204presents a large resistance to the line current and the charging currentof condensers 2|0, 2|I, 2|4 and 2|5, as well as the spacing impulse, isforced to traverse resistance 220 which reduces the current surgesuiciently to prevent relay 202 from breaking its right-hand or markingcontacts'.

Referring now to Fig. 3, a circuit is shown which combines some of thefeatures of the circuits shown in Figs. 1 and 2. Inthis case, two l,

its right-hand or marking contacts, positive battery is connectedthrough the upper winding of relay 302, unidirectional device 304, lineconductor 305, station S, to negative battery over line conductor 300.Unidirectional device 304 is connected in such a way that itsYresistance is low to the current in the circuit described above.Unidirectional device 308 in series with resistance 303 is connected inparallel with the upper Winding of relay 302 and unidirectional device'304, but device 308 is poled inthe opposite direction to device 304 andthe circuit Velement comprising unidirectional device 308 and resistanceS03 is of sufficiently high impedance during the marking impulse to havea negligible shunting effect on the upper winding of relay 302. As inthe previous cases a parallel circuit is provided to energize the lower,balancing winding of receiving relay 302, this circuit being traced frompositive battery through the right-hand contacts of relay 30|, throughthe lower winding of Vrelay 302 to ground through balancing network 3|6. As in the previous cases, the transient current due to the markingcharge of line capacities 3|0, 3| l, 3M and SI5 traverses the upperwinding of relay 302 but tends to keep the armature of relay 302 firmlyagainst its right-hand contact,

Cil

When relay 301 closes its left-hand contacts to ksend a spacing chargewhich is in the opposite direction to :the marking charge,unidirectional device 304 effectively .prevents the charging current ofcondensers 3:10, 311, 314 and 315 from traversing the upper winding ofrelay 302, while unidirectional device 308 and resistance 303 provide alow resistance parallel path so that the spacing impulse is transmittedto station S.

nbecause it removes the unidirectional device from the line circuit. Inthis case, when sending relay 401 closes its right-hand contacts,positive battery is connected through the upper windings of vreceivingrelay 402 and break relay 403 in series, through variable resistance404, line conductor 405, substation S, to negative battery over lineconductor 405. When the condensers 410, 411, 414 .and 415 are charged tothis condition, the transient current through the line windings ofrelays 402 and 403 keeps the armatures of these 1^elays on theirright-hand or marking contacts. A parallel circuit is traced frompositive battery through the right-hand contacts of relay 401, lowerwindings of relays 402 and 403, resistance-408, to ground throughresistance 416. A network consisting of condenser 418, resistance 419,and unidirectional device 41'.' is also connected in this circuit butdue to the poling of unidirectional device 411, no appreciable currentiiowsin it.

When relay 501 closes its left-hand contacts to send a spacing impulse,line condensers 410, 411, 414 and 415 charge through the upper windingsof relays 402 and 403, sending a transient wave through these relays,which would ordinarily cause them to break their right-hand or markingcontacts. In this case, however, the current through the lower windingsof relays 402 and 403 and the balancing network finds a low impedancepath through unidirectional device 4i? and the large condenser 418. Atransient current, therefore, flows through the lower windings oi relays402 and 403 which effectively neutralizes the transient in the upperwindings and prevents these relays from opening their righthandcontacts. Resistance 4 I 9 is provided to discharge condenser 418 afterthe circuit has reached a steady state.

In Fig. 5, an arrangement is shown for applying the features of theinvention to a composite telephone and telegraph circuit. In this case,as in Fig. 4, a unidirectional device is connected in the local circuitfor the balancing network of the receiving relay to provide balancingtransients during spacing impulses without introducing transmissionlosses. When transmitting relay 501 is actuated to marking, it closesits left-hand contacts and negative battery is connected through theupper winding of receiving relay 502, through the compositing set 553,

over line conductor 505, through compositing set 50i', the upper windingof receiving relay 503, to negative battery through the left-handcontacts oi relay 500. Thus, no current iiows in the line circuit duringmarking. At the same time, a parallel circuit is closed from negativebattery irough the left-hand contacts of relay 501 through the lowerwinding of relay 502, and the duplex balancingcircuitto ground. The cur-Arent in this circuit vholcls relay 502 in marking position.

The balancing circuit in this instance may comprise the usual linebalancing resistances 511 and 514 and capacity 513 and also a separatebalancing unit V504 for balancing the impedance of the compositing set503 in the line circuit.

Unidirectional device 512 is connected in parallel with the llowerwinding of relay 502 and resistance 511 .in such a way that when relay501 `operates to spacing, condenser 513 will be charged ,to a positivepotential with respect to ground through the unidirectional device 512and the current through the lower winding of relay 502 which tends tooperate the relay to spacing will be of very small value. Line condenser556 then will also be charged to positive potential, but the linecurrent which traverses the upper winding of relay 502 is in a directionto cause the relay to remain rrnly upon its righthand or markingcontacts.

When relay 501 closes its left-hand contacts to transmit a markingimpulse, line capacity 505 is charged to a negative potential throughthe upper windingof relay 502. In this case, however, the transientcurrent in the upper Winding or" relay 552 is in a direction to tend tooperate relay to spacing; however, condenser 513 now charges in adirection through the lower winding of relay 502 to hold the relay inmarking position. A heavy transient current is therefore generated inthe lower winding of Arelay 502 which opposes the transient in the upperwinding and eectively prevents relay 502 from opening its right-handcontacts.

In a similar manner, relay 50S may transmit marking and spacing impulsesto receiving relay 552 without causing relay-508 to open itsleftcontacts because of the similar circuit arrangement involvingbalancing network 510, unidirectional device 516, condenser 51'1, andresistance 558. When relay 509 is operated to spacing, the line windingo relay 502 will oppose the biasing winding and the line current Will besufficient to operate the relay to spacing.

For a complete system extending from the subscribers station S in thevarious figures to ,another similar subscribers station, the entiresystem shown in the drawings, except relays 101 and 102 in Fig. l andcorresponding relays in the other figures, may be duplicated. Thus, forexample in Fig. l, the contacts S and M of relay 102 would constitutesending contacts for the other line circuit corresponding to thecontacts of relay 101; one winding of relay 101 would be connected tothe incoming line and the other winding would be included in a biasingcircuit similar to that including the lower winding of relay 152 and thenetwork IIB. In Fig. 5, the windings or relay 501 may be connected likethose of relay 50S, and the contacts of relay 502 like those oi relay509 for operation with a line similar to line 555.

W hat is claimed is:

l. A polarized signal relay having two windings for producing opposedfluxes resulting in an operating ilux, a signaling circuit including aline circuit and balancing circuit means, said windings being connectedin said signaling circuit, and unidirectional circuit means andimpedance means in multiple relation and associated with one of saidwindings to prevent a discharge of said signaling circuit from reversingthe direction ofsaid .operating flux.

. balancing Awindings respectively, signaling means connected to thelother side of said windings for alternately charging and dischargingsaid signaling circuit, and unidirectional circuit means and impedancemeans in multiple relation and connected to one of said windings toprevent said charging and discharging of the signaling circuit fromoperating the relay armature by proportioning the discharging currentsthrough said Win-dings without substantially affecting the chargingcurrents therethrough.

3. A polarized signal relay having a line wind-f ing and a secondWinding, a signaling circuit including a line circuit and balancingcircuit means,

said windings being included in said signaling circuit, signaling meansfor oppositely energizing said win-dings to produce a resultantoperating flux during sending of a current impulse and for energizingsaid second winding to produce a holding flux in the same direction asthe operating ux during sending of a no-current impulse, asymmetriccircuit means including a unilateral device and a by-path thereforconnected to one of said windings to cause during a no-current impulsethe iluX produced by said second winding to be larger than the uXproduced by a surge current from the line circuit through said linewinding.

4. A polar signaling relay, a line circuit including a Winding of saidrelay, a balancing circuit including another winding of said relay,signal transmitting means connected to apply alternating potentials ofopposite polarities simultaneously to both of said circuits therebyproducing an alternating current through one of said windings, and amultiple network including unidirectional circuit means connected 'tosaid circuit including the other of sai-d windings for reducing thecurrent ilowing therein during the application of one of said potentialswith respect to the current flowing therein during the application ofthe other potential to prevent said relay from operating during saidapplications of potentials.

5. The combination in accordance with claim 4 in which said multiplenetwork comprises a unidirectional cell for passing currents in onedirection therethrough and opposing currents in the other direction, andan impe-dance branch for ley-passingv the said opposed currents aboutsaid cell and limiting them.

6. A polar signaling relay, a lineV circuit including a winding of saidrelay, a balancing circuit including another winding oi said relay, saidcircuits being connected at a common apex point, signaling means foralternately applying opposite voltage polarities to said apex point andfor thereby producing an alternating current in one of said windings, amultiple network including a unidirectional cell and an impedance branchand connected to limit the current flow in one direction during one halfcycle through the other of said windings with respect to the currentflow in the opposite direction during the other half cycle therethroughso that the resultant flux produced by said windings will be continuousin one direction during the operation of said signaling means.

7. A polar signaling relay, a line circuit including a line winding ofsai-d relay, a balancing circuit including another winding of saidrelay, said circuits being connected to a common apex point, signalingmeans for alternately applying opposite 2 in which said unidirectionalcircuit means comprises an impedance serially connected to one of saidwindings and an asymmetric cell con- Y nected in multiple relation tosaid one winding.

9. The combination in accordance with claim 6 in which said impedancebranch is serially included in said line circuit for control of thenormal line current strength and said unidirectional cell is connectedin a by-path about the relay winding included in said line circuit toprovide a low impedance path for surge currents i in said signalingcircuit of direction opposite that of the normal line current.

10. The combination in accor-dance with claim 4 in which said multiplenetwork is connected in said balancing circuit and comprises a currentlimiting branch for balancing the currents through said windings whenone of said signaling Vpotentials is applied simultaneously to both ofsaid windings and further comprising a rectifying device connected inparallel to sai-d branch for admitting additional current through saidother winding when the other potential is applied.

l1. The combination in accordance with claim 6 in which said multiplenetwork is connected in said balancing circuit and further includestransient charge absorbing means serially connected to sai-dunidirectional cell and effective substantially coincidentally withtransient discharges in said line circuit so that the said resultant uxwill be continuously unidrected and of substantially constant strengthduring the operation of said signaling means. Y

l2. A polarized signaling relay, a line circuit including a winding ofsaid relay, a balancing circuit including another winding of sai-drelay, said circuits being connected to a common apex point, signalingmeans for alternately applying diierent voltage polarities to said apexpoint, a condenser and a rectifying device connected in a series circuitincluded in said balancing circuit, a discharge impedance connectedacross said condenser and a balancing impedance connected in Vmultiplerelation to said rectifying device.

13. A polar signalingY relay, a high capacity signaling circuitincluding a winding of said relay,V

signaling means for alternately charging and discharging said circuit, aunilateral device in series connection with sai-d winding to at leastpartly prevent the discharge of said signaling circuit from passingthrough said winding, a second unilateral device in multiple connectionwith said winding to at least partly by-pass said discharge.

14. A polarized signaling relay, a line signaling circuit including aline circuit, balancing circuit means, and windings of said relay, amultiple network included in said balancing circuit and comprising animpedance branch for control of normal current in said balancing circuitand an asymmetric impedance branch including a unidirectional .deviceand transient charge absorbing means in series relation.

15. A polarized signaling relay, a signaling circuit includingtransmitting means, a line circuit, a balancing circuit and windings ofsaid relay, a multiple network included in said balancing circuit andcomprising a current limiting impedance branch, and an asymmetricimpedance branch including a unidirectional .device and transient chargeabsorbing means in series relation for apportioning the normal andtransient currents in said windings to prevent kick-off of said relay.

16. A telegraph system including a polarized signaling relay havingopposing windings for producing a resultant operating ux, a line circuitincluding said windings, balancing circuit means included in said linecircuit, and signaling means for charging said line circuit and producea resultant flux in said relay in one direction and for alternatelydischarging said line circuit, an asymmetric network including aunilateral device connected with said line circuit for preventing thesaid discharging of the line circuit from reversing said resultant ux.

17. The combination in accordance with claim l in which said impedancemeans is serially included in said signaling circuit.

18. In a telegraph signal repeating system, a relay Winding for passingimpulses between a transmitting circuit and a capacitance circuit, and amultiple branch circuit including an asymmetric branch and connected tosaid winding to permit normal impulse currents to pass through saidwinding and to reduce transient currents through said winding due to thecapacitance of said capacitance circuit.

19. In a telegraph signal repeating system, a relay having an operatingwinding for passing impulses between a transmitting circuit and a signalline circuit including substantial capacitance, and having a balancingwinding for passing impulses from said transmitting circuit to abalancing line circuit including substantial capactance, and a multiplebranch circuit including an asymmetric branch and connected to one ofsaid windings to permit normal impulse currents to pass through said onewinding and to reduce transient currents through said one winding due tothe capacitance of the associated line circuit.

20. In a signal repeating system, a relay winding connected between atransmitting circuit and a capacitance circuit, and a multiple branchcircuit having an impedance branch and an asymmetric branch andconnected to said winding to permit the ow through said winding in onedirection and to substantially reduce the flow through said winding inthe other direction of transient currents between said transmittingcircuit and said capacitance circuit.

21. In a telegraph signal repeating system, a relay having an operatingwinding for passing impulses between a transmitting circuit and a signalline circuit including substantial capacitance, and having a balancingwinding for passing impulses from said transmitting circuit to abalancing line circuit including substantial capacitance, and a multiplebranch circuit including an impedance branch and an asymmetric branch toprovide a low and a. relatively high impedance to transient currents ineither direction through said multiple circuit, one of said windingsbeing connected to pass transient currents in both directions from itsassociated line circuit, and said multiple branch circuit beingconnected to the other winding to proportion the transient currents dueto said capacitances through said windings in each direction forpreventing said relay from responding to operations of said transmittingcircuit.

WALTER W. CRAMER. GEORGE C. CUNDVIINGS.

